1 Imperative Queues

Version: 5.1.3

This module provides a simple mutable queue representation, first-in/first-out only. Operations on queues mutate it in a thread-unsafe way.

Produces an empty queue.

(enqueue! q v) → void?

q : queue/c

v : any/c

Adds an element to the back of a queue.

Removes an element from the front of a nonempty queue, and returns that element.

Examples:
(define q (make-queue))

> (enqueue! q 1)
> (dequeue! q)
1
> (enqueue! q 2)
> (enqueue! q 3)
> (dequeue! q)
2
> (dequeue! q)
3

queue : queue/c

Returns an immutable list containing the elements of the queue in the order the elements were added.

Examples:
(define queue (make-queue))

> (enqueue! queue 8)
> (enqueue! queue 9)
> (enqueue! queue 0)
> (queue->list queue)
'(8 9 0)

queue : queue/c

Returns the number of elements in the queue.

Examples:
(define queue (make-queue))

> (queue-length queue)
0
> (enqueue! queue 5)
> (enqueue! queue 12)
> (queue-length queue)
2
> (dequeue! queue)
5
> (queue-length queue)
1

q : queue/c

Recognizes whether a queue is empty or not.

v : any/c

This predicate recognizes queues.

Examples:
> (queue? (make-queue))
#t
> (queue? 'not-a-queue)
#f

queue : queue?

Returns a sequence whose elements are the elements of queue.

These contracts recognize queues; the latter requires the queue to contain at least one value.

1	Imperative Queues
2	Growable Vectors
3	Orders and Ordered Dictionaries
4	Splay Trees
5	Skip Lists
6	Interval Maps
7	Binary Heaps